1 /* strspn (str, ss) -- Return the length of the initial segment of STR
2 which contains only characters from SS.
4 Copyright (C) 1994-1997, 2000, 2002, 2003, 2004, 2005
5 Free Software Foundation, Inc.
6 This file is part of the GNU C Library.
7 Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu>.
8 Bug fixes by Alan Modra <Alan@SPRI.Levels.UniSA.Edu.Au>.
9 Adopted for x86-64 by Andreas Jaeger <aj@suse.de>.
11 The GNU C Library is free software; you can redistribute it and/or
12 modify it under the terms of the GNU Lesser General Public
13 License as published by the Free Software Foundation; either
14 version 2.1 of the License, or (at your option) any later version.
16 The GNU C Library is distributed in the hope that it will be useful,
17 but WITHOUT ANY WARRANTY; without even the implied warranty of
18 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
19 Lesser General Public License for more details.
21 You should have received a copy of the GNU Lesser General Public
22 License along with the GNU C Library; if not, see
23 <http://www.gnu.org/licenses/>. */
25 #include "_glibc_inc.h"
30 movq %rdi, %rdx /* Save SRC. */
32 /* First we create a table with flags for all possible characters.
33 For the ASCII (7bit/8bit) or ISO-8859-X character sets which are
34 supported by the C string functions we have 256 characters.
35 Before inserting marks for the stop characters we clear the whole
37 movq %rdi, %r8 /* Save value. */
38 subq $256, %rsp /* Make space for 256 bytes. */
39 movl $32, %ecx /* 32*8 bytes = 256 bytes. */
41 xorl %eax, %eax /* We store 0s. */
46 movq %rsi, %rax /* Setup stopset. */
48 /* For understanding the following code remember that %rcx == 0 now.
49 Although all the following instruction only modify %cl we always
50 have a correct zero-extended 64-bit value in %rcx. */
52 /* Next 3 insns are 6 bytes total, make sure we decode them in one go */
55 movb (%rax), %cl /* get byte from stopset */
56 testb %cl, %cl /* is NUL char? */
57 jz L(1) /* yes => start compare loop */
58 movb %cl, (%rsp,%rcx) /* set corresponding byte in stopset table */
60 movb 1(%rax), %cl /* get byte from stopset */
61 testb %cl, %cl /* is NUL char? */
62 jz L(1) /* yes => start compare loop */
63 movb %cl, (%rsp,%rcx) /* set corresponding byte in stopset table */
65 movb 2(%rax), %cl /* get byte from stopset */
66 testb %cl, %cl /* is NUL char? */
67 jz L(1) /* yes => start compare loop */
68 movb %cl, (%rsp,%rcx) /* set corresponding byte in stopset table */
70 movb 3(%rax), %cl /* get byte from stopset */
71 addq $4, %rax /* increment stopset pointer */
72 movb %cl, (%rsp,%rcx) /* set corresponding byte in stopset table */
73 testb %cl, %cl /* is NUL char? */
74 jnz L(2) /* no => process next dword from stopset */
76 L(1): leaq -4(%rdx), %rax /* prepare loop */
78 /* We use a neat trick for the following loop. Normally we would
79 have to test for two termination conditions
80 1. a character in the stopset was found
82 2. the end of the string was found
83 But as a sign that the character is in the stopset we store its
84 value in the table. But the value of NUL is NUL so the loop
85 terminates for NUL in every case. */
87 /* Next 3 insns are 9 bytes total. */
88 /* .p2align 4,,9 would make sure we decode them in one go, */
89 /* but it will also align entire function to 16 bytes, */
90 /* potentially creating largish padding at link time. */
91 /* We are aligning to 8 bytes instead: */
94 addq $4, %rax /* adjust pointer for full loop round */
96 movb (%rax), %cl /* get byte from string */
97 testb %cl, (%rsp,%rcx) /* is it contained in skipset? */
98 jz L(4) /* no => return */
100 movb 1(%rax), %cl /* get byte from string */
101 testb %cl, (%rsp,%rcx) /* is it contained in skipset? */
102 jz L(5) /* no => return */
104 movb 2(%rax), %cl /* get byte from string */
105 testb %cl, (%rsp,%rcx) /* is it contained in skipset? */
106 jz L(6) /* no => return */
108 movb 3(%rax), %cl /* get byte from string */
109 testb %cl, (%rsp,%rcx) /* is it contained in skipset? */
110 jnz L(3) /* yes => start loop again */
112 incq %rax /* adjust pointer */
116 L(4): addq $256, %rsp /* remove stopset */
117 subq %rdx, %rax /* we have to return the number of valid
118 characters, so compute distance to first
119 non-valid character */
123 libc_hidden_def(strspn)